Information; About Satellite Navigation; How Satellite Navigation Works; Line Of Sight - Magellan RoadMate 300 Reference Manual

Information

Information

About Satellite Navigation

Global satellite navigation is an exciting technology, providing enhanced productivity and accuracy in a vast number
of industries. It adds a new level of enjoyment and safety to a wide range of navigation, sports, and recreational
activities.
A Global Navigation Satellite System (GNSS) is a network of satellites that transmit high-frequency radio signals
containing time and distance data that can be picked up by a receiver, allowing users to pinpoint their precise
locations anywhere around the globe.
There are two Global Navigation Satellite Systems in operation: the U.S. Global Positioning System (GPS) and the
Russian GLObal NAvigation Satellite System (GLONASS). These systems are constantly being upgraded to meet
higher standards of reliability. A third GNSS named GALILEO, after the Italian astronomer of the early 1600s, is
being developed in Europe specifically to provide a higher standard of integrity and reliability, required to ensure the
safety of lives during transport by air, land and sea, without the use of additional augmentation systems.
While the GPS and GLONASS satellite networks are being developed to achieve maximum performance, Satellite-
Based Augmentation Systems (SBAS) have been established to provide improved accuracy. SBAS provides
differential signal corrections for GPS and GLONASS transmissions with the use of ground stations and
geostationary satellites in specific regions. This is GNSS-1, the first phase in establishing the required integrity for
high-precision satellite navigation.
GNSS-2 requires the launching of new satellites into orbit and a complete upgrade of the existing satellite systems.
This second phase is already well underway. GALILEO, scheduled to begin service in 2008, is being developed to
meet the standards of GNSS-2 for rapid and reliable, certified precision positioning.

How Satellite Navigation Works

Global navigation satellites continuously transmit time and distance information as they orbit the earth in a precise
formation. Navigation satellite receivers use this information to calculate an exact location through triangulation.
Every point on Earth is identified by two sets of numbers called coordinates. These coordinates represent the exact
point where a horizontal line, known as latitude, crosses a vertical line, known as longitude. The receiver locks on to
at least three satellites and uses the information received to determine the coordinates of the receiving device.
By comparing the time the signals were transmitted from the satellites and the time they were recorded, the receiver
calculates how far away each satellite is. The distance of the receiver from three or more satellites reveals its
position on the surface of the planet. With these distance measurements, the receiver might also calculate speed,
bearing, trip time, distance to destination, altitude, and more.
The satellite-navigation device may display its position as longitude/latitude, Universal Transverse Mercator (UTM),
Military Grid (MG), or simply as a point on an electronic map. Many Thales Navigation receivers provide
comprehensive mapping data, making satellite navigation an easy tool to enhance your recreational and industrial
activities.

Line of Sight

Satellite-navigation receivers operate by line of sight with global-positioning satellites. This means that at least three
satellites must be in "view" of a receiver in order to calculate longitude and latitude. A fourth satellite must also be
within line of sight to calculate altitude. On average, eight satellites are continuously within line of sight of every
position on Earth; the more satellites in view, the more accurate the positioning.
Though the radio signals of navigation satellites will pass through clouds, glass, plastic, and other lightweight
materials, satellite-navigation receivers will not work underground or in other enclosed spaces.
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